Method for recovering lithium
To provide a method for recovering lithium, that is capable of efficiently recovering lithium without containing impurities, such as phosphorus and fluorine, from a lithium-containing solution containing lithium hexafluorophosphate and separated from a lithium ion battery. In the present invention, alkali hydroxide is added to the lithium-containing solution and the solution is made to have pH 9 or more, a precipitate of a phosphate and a fluoride salt is formed, the formed precipitate is separated and removed, and then lithium is recovered from filtrate.
1. A method for recovering lithium from a lithium-containing solution containing lithium hexafluorophosphate separated from a lithium ion battery, the method comprising:
a precipitate formation process of adding alkali hydroxide to the lithium-containing solution to cause the lithium-containing solution to have pH 9 or more, and forming a precipitate of a phosphate and a fluoride salt; and
a lithium recovery process of recovering lithium from filtrate after separating and removing the precipitate formed in the precipitate formation process.
2. The method for recovering lithium according to claim 1 , wherein the alkali hydroxide is potassium hydroxide.
3. The method for recovering lithium according to claim 1 , wherein the lithium recovery process includes
an extraction process of adding an alkali solution to the filtrate to adjust pH to 8 to 13, and allowing an acidic extractant to be in contact with the filtrate to extract lithium ions, and
a stripping process of allowing the acidic extractant having extracted the lithium ions in the extraction process to be in contact with an acid solution having pH 3 or less to strip the lithium ions.
4. The method for recovering lithium according to claim 3 , wherein the lithium recovery process includes a scrubbing process of scrubbing the acidic extractant having extracted the lithium ions in the extraction process, and performs the stripping process after scrubbing.
5. The method for recovering lithium according to claim 4 , wherein the lithium recovery process further includes a lithium carbonate deposition process of adding a carbon dioxide gas or a water-soluble carbonate to a stripping liquid containing the lithium ions obtained in the stripping process, and depositing a lithium carbonate.
6. The method for recovering lithium according to claim 1 , wherein the lithium recovery process adds an alkali carbonate solution to the filtrate, and deposits a lithium carbonate to recover lithium.
7. The method for recovering lithium according to claim 1 , wherein the precipitate formation process adds the alkali hydroxide to a lithium-containing solution that has been cleaned with water in advance.